Bone tissue engineering and bone development hold great promise in the field of tissue engineering and orthopedics. One of the major challenges of tissue engineering, including bone, is to form three-dimensional tissues and organs ex vivo. We hypothesized that the combination of: a. Transduction of Adult Mesenchymal Stem cells with BMP2 gene, and b. Application of physiological forces, can be utilized for ex vivo engineering of functional bone. This hypothesis is driven from two lines of prior successful investigations by the Israeli and American Pi's involved in the proposal, to achieve a synergistic outcome with clinical relevance. We intend to use engineered cells grown on polymeric scaffolds to form three dimensional ex vivo bone tissue in a loading bioreactor device. BMP-2 gene expression will be achieved in human Adult Mesenchymal Stem Cells (AMSCs) by non-viral Amaxa Nucleofector gene delivery system and in murine MSCs will be achieved by tetracycline (tet) controlled expression system. In order to promote ex vivo bone tissue growth, we intend to use a bioreactor, which applies quantitative mechanical forces of physiological amplitudes and frequencies, thus imitating natural skeletal movements. Thus, combining the four elements: AMSCs, a potent osteogenic gene, and controlled loading forces ex vivo, will enable us to produce a physiological bone organ culture system leading to functional osteogenic tissue formation. Our hypothesis will be tested by pursuing the following specific aims: 1) Genetically engineering of human AMSCs to express hBMP2; 2) Culturing of hBMP2-expressing AMSCs in ex vivo bioreactor system on bioactive polymeric scaffold. 3) Implanting the engineered osteogenic tissue in order to assess in vivo function. Collectively, our novel concept should lead to the ex vivo generation of osteogenic tissue, thus establishing a powerful system for bone tissue engineering applications.